1. Field of the Invention
The present invention is directed to a system and method of deriving temperature distributions in large combustion chambers such as kilns and boilers. A stepwise temperature distribution is measured by a single ended acoustic device along any desired line of measurement.
2. Description of the Prior Art
Temperature measurements are necessary for the control of industrial processes. Temperature profiles or distributions are considered to be very useful for improvements in control and in energy savings and in cases such as a recovery boiler, also useful in minimizing dust formation. Commonly thermocouples and radiation pyrometers are used for temperature measurements.
There are limitations and disadvantages associated with present techniques in the hostile environments of kilns and furnaces. Commonly employed thermocouples do not survive well in a hostile chemical environment and it is difficult to protect long lead wires with proper insulation capable of withstanding high temperatures. Radiation pyrometers have the disadvantage that they are incapable of providing information on temperature variations within their field of view. The presence of dust, excessive flame brightness, absence of a target in the region of interest add to further uncertainties.
The acoustic method is based on the fact that the speed of sound in a gas is a unique function of temperature. Even though the relation between the speed of sound and temperature has been known for a long time, and has been suggested as a means of temperature measurement (Mayer 1873) it is only recently that the method has seen some development (Hedrich & Pardue 1955; Plumb & Cataland 1966; Lynnworth & Patch 1970; Gopalsami & Raptis 1984; Wadley et al 1986; Green 1986; O'Fallon 1984). Whereas most investigations (Lynnworth & Patch 1970; Gopalsami & Raptis 1984; Wadley et al 1986) dwell on the method as applied to the measurement of temperature field in a flowing gas medium using acoustic tomography. O'Fallon (1984) gives a review of the state of the art as applicable to the measurement of temperature in coal gasification systems.